The standard picture of evolution, is externalist: a causal arrow runs from environment to organism, and that arrow explains why organisms are as they are (Godfrey-Smith 1996). Natural selection allows a lineage to accommodate itself to the specifics of its environment. As the interior of Australia became hotter and drier, phenotypes changed in many lineages of plants and animals, so that those organisms came to suit the new conditions under which they lived. Odling-Smee, Laland and Feldman, building on the work of Richard Lewontin, have shown that while sometimes appropriate, this is an inadequate conception of the relationship between organisms and the environments in which they live. Over time organisms alter their environment as well as being altered by their environments (Lewontin 1982; Lewontin 1983; Lewontin 1985). For example, animals modulate the effects of their physical and biological environment by building shelters: the beaver’s dam and lodge system, and termite mounds are two famous cases of animal structures, but they are few of many. There are many thousands of animals which make nests, burrows and other shelters. Likewise, animals make tools that give them access to resources from which they would otherwise be excluded: thus the Galapagos woodpecker finch uses a cactus needle to extract insects from crevasses in bark — insects that they would otherwise be unable to catch (Tebbich, Taborsky et al. 2001). Tool making is not as common as shelter-making, but it is common. For example many animals make traps: there are many species of pit-making antlions. Thus in part organisms make the world in which they live. They partially construct their own niches. Odling-Smee, Laland and Feldman argue that this has five major and under-appreciated consequences for biological theory.